Telebit T3000 Reference Manual page 89

&C(n) Data Carrier Detect (DCD) Control
Range: 0-3
Default: O
See also: S47
The &C command controls the DCD signal
interpretation to the local DTE.
&C Same as &CO.
&CO The DCD signal is always ON.
&C1 When the local modem detects a carrier from the
remote modem, the DCD signal goes ON after the
CONNECT result code is sent to the DTE. The
DCD signal goes OFF when the carrier is dropped.
&C2 The DCD signal is always ON, except when it is
pulsed OFF for a period of time specified by the
S47 register while disconnecting a call.
&C3 DCD is the inverse of the Clear to Send (CTS)
signal.
&D(n) Data Terminal Ready (DTR) Interpretation
Range: 0-3
Default: 0
See also: &Q(n), S25
The &D command defines the DTR signal
interpretation from the DTE. The &Q command can
override the behavior dictated by this command,
which will not change the current value of the &D
command. The modem responds to changes in the
DTR signal as follows:
&D Same as &DO.
&DO The modem ignores DTR and assumes that DTR
is always ON.
5-14 AT Command Descriptions